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  Organic light-emitting device and organic light-emitting displayUSPTO Application #: 20060290613Title: Organic light-emitting device and organic light-emitting display Abstract: An organic light-emitting device including: a light emitting diode that emits light by a signal current; a driving thin film transistor connected between a source voltage and a light emitting diode and connected at its drain to the light emitting diode and a current source, and that supplies the signal current to the light emitting diode depending on display data; a storage capacitor connected between the source voltage and a gate of the driving thin film transistor, and that stores the display data depending on a display data signal; a first switching unit connected between the drain of the driving thin film transistor and a data driver and connected at its gate with a first scan line, wherein the first switching unit and selects the data signal; a second switching unit connected between the gate and the drain of the driving thin film transistor and connected at its gate with a second scan line wherein, the second switching unit drives the driving thin film transistor; and a third switching unit connected between the drain of the driving thin film transistor and the light emitting diode and connected at its gate with a third scan line, wherein the third switch unit selects the signal current applied to the light emitting diode. (end of abstract) Agent: Mckenna Long & Aldridge LLP Song K. Jung - Washington, DC, US Inventors: Soon Kwang Hong, In Gyo Seo USPTO Applicaton #: 20060290613 - Class: 345076000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060290613. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This nonprovisional application claims the benefit of Korean Patent Application No. 10-2005-0055570, filed on Jun. 27, 2005, which is hereby incorporated by reference for all purposes as if fully set forth herein. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an organic light-emitting device and an organic light-emitting display using the same. [0004] 2. Discussion of the Related Art [0005] An organic light-emitting diode (OLED) is an active light-emitting device that excites a phosphor and emits light by a recombination of electrons and holes. An organic light-emitting display including the organic light-emitting diode may be used in a wall mounted device or a portable device due to its fast response speed, low direct-current driving voltage, and ultra thinness, in comparison to a passive light-emitting device needing a separate light source such as a liquid crystal display. [0006] The organic light-emitting diode produces a color using pixels where red, green, and blue sub pixels combine to a color. In a method of driving the subpixel, the organic light-emitting diode may be classified into a passive matrix organic light-emitting diode (PMOLED), and an active matrix organic light-emitting diode (AMOLED) employing a driving method using a thin film transistor (TFT). [0007] The driving method of the active matrix organic light-emitting diode (AMOLED) may be classified into a current driving method, a voltage driving method, and a digital driving method. [0008] FIG. 1 is an equivalent circuit diagram illustrating a conventional current driving active matrix organic light-emitting device (AMOLED), and FIG. 2 is a driving timing diagram of FIG. 1. [0009] Referring to FIG. 1, the conventional organic light-emitting device 50 includes a first TFT (M2), a second TFT (M3), a first switch (S/W5), a second switch (S/W6), a storage capacitor (Cst), and an organic light-emitting diode (OLED). [0010] The first and second TFTs (M2 and M3) have a mirror structure to supply a constant current to the organic light emitting diode (OLED), are connected at their sources with a source voltage (VDD), and are connected at their gates to the storage capacitor (Cst). The drain of the first TFT (M2) connects to the organic light emitting diode, and the drain of the second TFT (M3) connects between the first and second switches (S/W5 and S/W6). [0011] Referring to FIGS. 1 and 2, the first and second switches (S/W5 and S/W6) are series connected between the gates of the first and second TFTs (M2 and M3) and a data line. The first and second switches (S/W5 and S/W6) are connected at their gates with a scan line, and switch the data signal (data n) by the scan signal (scan n) of FIG. 2 applied through the scan line. [0012] The storage capacitor (Cst) is between the gates of the first and second TFTs (M2 and M3) and the second switch (S/W6), and stores the data voltage from the source voltage (VDD) by the data signal (data[n]) of FIG. 2. [0013] The organic light-emitting diode (OLED) emits light by a current generated from the first TFT (M2) driven by the data voltage stored in the storage capacitor (Cst). A gray level of the organic light-emitting diode (OLED) is determined by the amount of the signal current. For a high gray level, a larger signal current is supplied to the organic light-emitting diode (OLED), and for a low gray level, a smaller signal current is supplied to the organic light-emitting diode (OLED). [0014] However, the conventional organic light-emitting device has a drawback in that when a low gray level is displayed, in comparison a current supplied from a data driver is dozens of nA. Then the storage capacitor cannot be charged with a desired data voltage due to a data line load on the data line between the data driver and a pixel before the storage capacitor of the pixel is charged with the desired data voltage. [0015] In other words, the conventional organic light-emitting device has a drawback in that when a low gray level is displayed, due to the data line load, the storage capacitor (Cst) cannot be sufficiently charged with a current of dozens of nA during a gate on time of several msec. [0016] As a result, the conventional organic light-emitting display having a pixel circuit including the organic light-emitting device has a drawback in that it cannot be put to practical use due to the deterioration of the capability to display a low gray level. SUMMARY OF THE INVENTION [0017] Accordingly, the present invention is directed to organic light-Emitting device and organic light-emitting display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. [0018] An advantage of the present invention is to solve at least the problems and disadvantages of the background art. [0019] Another advantage of the present invention is to provide an organic light-emitting device and an organic light-emitting display using the same, in which when a low gray level is displayed, a storage capacitor is sufficiently charged, thereby improving a capability to display low gray levels. [0020] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. [0021] To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an organic light-emitting device including: a light emitting diode that emits light by a signal current; a driving thin film transistor connected between a source voltage and a light emitting diode and connected at its drain to the light emitting diode and a current source, and that supplies the signal current to the light emitting diode depending on display data; a storage capacitor connected between the source voltage and a gate of the driving thin film transistor, and that stores the display data depending on a display data signal; a first switching unit connected between the drain of the driving thin film transistor and a data driver and connected at its gate with a first scan line, wherein the first switching unit and selects the data signal; a second switching unit connected between the gate and the drain of the driving thin film transistor and connected at its gate with a second scan line wherein, the second switching unit drives the driving thin film transistor; and a third switching unit connected between the drain of the driving thin film transistor and the light emitting diode and connected at its gate with a third scan line, wherein the third switch unit selects the signal current applied to the light emitting diode. [0022] In another aspect of the present invention, an organic light-emitting device including: a storage capacitor that stores a data voltage from a source voltage when a reference current and a data current are sunk depending on a data signal; a driving thin film transistor that receives the data voltage depending on a scan signal and supplying the reference current and the data current corresponding to the data voltage; a reference current source that outputs the reference current supplied from the driving thin film transistor; a light emitting diode that emits light by the data current supplied from the driving thin film transistor; and a switching unit that switches the data signal or the data current according to the scan signal. Continue reading... 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